Programmable-step, high-resolution frequency synthesizer which substantially eliminates spurious frequencies without adversely affecting phase noise

Abstract

Abstract A frequency synthesizer is described which operates over a wide frequency range at high resolution and variable step size without trading off between spurious frequency rejection and phase noise suppression. The synthesizer includes a magnetically-turned YIG oscillator which generates a desired output frequency from a received tuning signal. The output signal is fed back into a phase locked loop which generates the tuning signal. The phase locked loop includes a harmonic mixer for mixing the output signal with a reference frequency F 2 . The mixer receives a base frequency signal and a harmonic select signal resulting in the generation of the reference signal, F 2 . The mixed signal is input to a programmable divider, then to a phase detector which receives another reference signal, F 1 . The phase detector output is the tuning signal which is coupled to the YIG oscillator. Both reference frequencies, F 1 and F 2 , are derived from a common base frequency. A base frequency source includes a voltage-controller oscillator coupled to another phase locked loop. This other phase locked loop receives two reference signals, F x and F y . Reference F x preferably is generated by a direct digital synthesizer that receives programmable tuning parameters. Reference F y may be generated with a fixed, switched or other frequency source. A microprocessor is included for selecting the programmable divider factors, the direct digital synthesizer tuning parameters, and other variable factors.

Inventors

• 👤 Paul L. Vella

Bibliographic Details